HBOC-301 in Porcine Kidney Normothermic Machine Perfusion and the Effect of Vitamin C on Methemoglobin Formation

Abstract

Normothermic machine perfusion (NMP) of kidneys in combination with an optimized perfusate composition may increase donor organ preservation quality, especially in the case of marginal donor grafts. Optimization of currently employed perfusates is still a subject of present research. Due to the advantages of being cell-free, easy to store, and having minimal antigenicity, hemoglobin-based oxygen carriers, such as HBOC-301 (Oxyglobin®, Hemoglobin Oxygen Therapeutics LLC, Souderton, PA, USA), offer an alternative to the commonly used perfusates based on packed red blood cells (pRBC). As previously described, using HBOC results in formation of methemoglobin (metHb) as an adverse effect, inducing hypoxic conditions during the perfusion. As a potential counterpart to metHb formation, the application of the antioxidant ascorbic acid (VitC) is of high interest. Therefore, this study was conducted in four experimental groups, to compare the effect of NMP with (1) HBOC or (3) pRBC, and additionally examine a beneficial effect of VitC in both groups (2) HBOC + VitC and (4) pRBC + VitC. All groups were subjected to NMP for 6 h at a pressure of 75 mmHg. Kidneys in the HBOC groups had a significantly lower renal blood flow and increasing intrarenal resistance, with reduced renal function in comparison to the pRBC groups, as demonstrated by significantly lower creatinine clearance and higher fractional sodium excretion rates. Clinical chemistry markers for tissue damage (LDH, lactate) were higher in the HBOC groups, whereas no significant histological differences were observed. Although the application of VitC decreased oxidative stress levels, it was not able to significantly increase the outcome parameters mentioned above in either group. This study demonstrated that HBOC-301 is inferior to pRBCs in our porcine kidney NMP model, independent of additional VitC administration. Oxidative stress and fragmentation of the hemoglobin polymers could be detected as a possible reason for these results, hence further research, focusing on the use of cell-free oxygen carriers that do not exhibit this complex of issues, is required.

Taurine as Antioxidant in a Novel Cell- and Oxygen Carrier-Free Perfusate for Normothermic Machine Perfusion of Porcine Kidneys

“…Euthanization was performed using 1 mL/kg BW pentobarbital (Narcoren, Merial GmbH, Hallbergmoss, Germany), cardiac arrest was testified, and a midline laparotomy was performed. Immediately after cardiac arrest, the vena cava was cannulated and 450 mL of venous blood were collected into sterile blood bags (Composelect ® , Fresenius Kabi Austria GmbH, Graz, Austria) each and prepared for pRBC production as described previously by our working group [ 16 ]. Kidneys were explanted simultaneously and weighed.…”

“…Kidneys were perfused simultaneously for 6 h at a mean arterial pressure (MAP) of 75 mmHg and at a temperature of 36.5 ± 0.1 °C, according to our established protocol [ 16 , 21 , 22 ].…”

“…As perfusion with whole blood or pRBC’s bears the risk of transfusion reactions through increased immunogenicity, inflammation, and hemolysis due to perfusion using systems with artificial surfaces, alternatives are the focus of experimental studies. In an attempt to replace pRBCs in our established NMP perfusate, we recently described the use of Hemoglobin-Based Oxygen Carrier-301 (HBOC-301, HBO2 Therapeutics, Souderton, PA, USA) [ 16 ] showing HBOC-301 to be inferior to pRBC’s in a 6 h porcine kidney NMP setting. Cell free solutions, such as Lifor, Aqix RS-I, University of Wisconsin solution (UW) and Steen solution have recently been described as alternative NMP perfusates in experimental studies [ 17 , 18 , 19 , 20 ].…”

“…In the current study, we aimed to investigate the use of Ecosol organ preservation solution (TX Innovations B.V., Gulpen, The Netherlands), originally developed for kidney SCS, as an alternative to our previously established pRBC-based NMP perfusate [ 16 , 21 , 22 ]. In contrast to HBOC-301, Ecosol is an acellular and oxygen carrier-free solution.…”

Controls of Central and Peripheral Blood Pressure and Hemorrhagic/Hypovolemic Shock

“…Subsequently, clinical trials for HBOCs are made available only through expanded access to save patients' lives when other interventions are not available. At present, HBOCs are approved for veterinary use in the United States, Russia, and the European Union [136]; however, none are FDA approved for human use.…”